Are sugars and starches dangerous for rabbits?
A current trend in the rabbit world is to believe that sugars and starches are dangerous for rabbits because they can cause ‘caecal dysbiosis’ and many owners avoid feeding fruit or root vegetables because of this. These foods are not dangerous and rabbits enjoy eating apples and carrots. They do not need to be excluded from the diet but should be fed in moderation because roots vegetables and fruit are fattening and calcium deficient.
Carbohydrate overload theory
The idea that sugars and starches are dangerous for rabbits probably originates from the ‘carbohydrate overload’ theory that originates from outbreaks of enteric disease in rabbits bred for intensive meat product. Clostridia species of bacteria have been diagnosed during some outbreaks. This bacterium causes a serious, often fatal, diarrhoea (enterotoxaemia). It requires glucose for toxin production. The idea of the carbohydrate overload theory is that a diet that is high in starch provides glucose to the caecal microflora for toxin production and this results in enterotoxaemia. Even in the scientific community of commercial rabbit nutrition, the theory is not universally accepted and even if it were true, it would only apply to young rabbits without an unbalanced caecal microflora. In adult rabbits, sugars and starches are absorbed in the small intestine. also, a high carbohydrate diet tends to be low in fibre and this is more likely to be the reason that commercial rabbits are so susceptible to enteric disease. They also live in crowded conditions where they are stressed and exposed to high loads of bacteria and other microorganisms, such as coccidia, in the environment.
Sugary treats for rabbits
Crowded, insanitary conditions are unusual for adult pet rabbits,. They are not prone to infectious enteritis. Common sense would say that sugary, starchy foods are highly unlikely to kill an adult pet rabbit by upsetting its caecal microflora. The rabbits that live on muesli mix and honey flavoured treats from the pet shop do not die from enterotoxaemia. They suffer from obesity instead. High calorie treats and muesli mix are never a good idea for rabbits. Unfortunately, some rabbit food manufacturers still produce and market them
'Caecal dysbiosis’ means a disruption in the balance of micro-organisms in the caecum, which is a contributory factor to enterotoxaemia. Enterotoxaemia is the reason why some antibiotics are dangerous for rabbits if they are given orally. They can selectively kill some bacteria and allow others (such as Clostridial species) to proliferate. The term 'caecal dysbiosis' is often used in relation to an idea that high dietary starch causes soft caecotrophs by altering the balance of micro-organisms within the caecum. This is unproven and unlikely as it does not fit with digestive physiology. In rabbits, simple monosaccharide sugars, such as glucose, fructose and galactose, are absorbed from the small intestine in a similar manner to other species. Starches in seeds, fruits, tubers and roots and are broken down to simple sugars during digestion and, as in other species, this reaction is catalysed by amylase secreted by the salivary glands and pancreas. Studies in rabbits fitted with catheters at the end of their small intestine (like a colostomy bag) have shown that nearly all starch is digested and absorbed before it reaches the caecum . Other studies have shown that dietary starch has been shown to have no influence on the chemical composition of caecal contents or on the production or composition of soft and hard faeces. Any link between high carbohydrate diets and soft caecotrophs is probably due to the indirect relationship of carbohydrate with fibre. High carbohydrate foods (such as fruit and cereals) tend to be low in indigestible fibre. The fibre content of caecotrophs affects their consistency, more fibre makes making them firmer.